+
+/**
+ * Auxiliary structure used for reading the snapshot image data and
+ * metadata from and writing them to the list of page backup entries
+ * (PBEs) which is the main data structure of swsusp.
+ *
+ * Using struct snapshot_handle we can transfer the image, including its
+ * metadata, as a continuous sequence of bytes with the help of
+ * snapshot_read_next() and snapshot_write_next().
+ *
+ * The code that writes the image to a storage or transfers it to
+ * the user land is required to use snapshot_read_next() for this
+ * purpose and it should not make any assumptions regarding the internal
+ * structure of the image. Similarly, the code that reads the image from
+ * a storage or transfers it from the user land is required to use
+ * snapshot_write_next().
+ *
+ * This may allow us to change the internal structure of the image
+ * in the future with considerably less effort.
+ */
+
+struct snapshot_handle {
+ loff_t offset; /* number of the last byte ready for reading
+ * or writing in the sequence
+ */
+ unsigned int cur; /* number of the block of PAGE_SIZE bytes the
+ * next operation will refer to (ie. current)
+ */
+ unsigned int cur_offset; /* offset with respect to the current
+ * block (for the next operation)
+ */
+ unsigned int prev; /* number of the block of PAGE_SIZE bytes that
+ * was the current one previously
+ */
+ void *buffer; /* address of the block to read from
+ * or write to
+ */
+ unsigned int buf_offset; /* location to read from or write to,
+ * given as a displacement from 'buffer'
+ */
+ int sync_read; /* Set to one to notify the caller of
+ * snapshot_write_next() that it may
+ * need to call wait_on_bio_chain()
+ */
+};
+
+/* This macro returns the address from/to which the caller of
+ * snapshot_read_next()/snapshot_write_next() is allowed to
+ * read/write data after the function returns
+ */
+#define data_of(handle) ((handle).buffer + (handle).buf_offset)
+
+extern unsigned int snapshot_additional_pages(struct zone *zone);
+extern int snapshot_read_next(struct snapshot_handle *handle, size_t count);
+extern int snapshot_write_next(struct snapshot_handle *handle, size_t count);
+extern void snapshot_write_finalize(struct snapshot_handle *handle);
+extern int snapshot_image_loaded(struct snapshot_handle *handle);
+
+/*
+ * This structure is used to pass the values needed for the identification
+ * of the resume swap area from a user space to the kernel via the
+ * SNAPSHOT_SET_SWAP_AREA ioctl
+ */
+struct resume_swap_area {
+ loff_t offset;
+ u_int32_t dev;
+} __attribute__((packed));
+
+#define SNAPSHOT_IOC_MAGIC '3'
+#define SNAPSHOT_FREEZE _IO(SNAPSHOT_IOC_MAGIC, 1)
+#define SNAPSHOT_UNFREEZE _IO(SNAPSHOT_IOC_MAGIC, 2)
+#define SNAPSHOT_ATOMIC_SNAPSHOT _IOW(SNAPSHOT_IOC_MAGIC, 3, void *)
+#define SNAPSHOT_ATOMIC_RESTORE _IO(SNAPSHOT_IOC_MAGIC, 4)
+#define SNAPSHOT_FREE _IO(SNAPSHOT_IOC_MAGIC, 5)
+#define SNAPSHOT_SET_IMAGE_SIZE _IOW(SNAPSHOT_IOC_MAGIC, 6, unsigned long)
+#define SNAPSHOT_AVAIL_SWAP _IOR(SNAPSHOT_IOC_MAGIC, 7, void *)
+#define SNAPSHOT_GET_SWAP_PAGE _IOR(SNAPSHOT_IOC_MAGIC, 8, void *)
+#define SNAPSHOT_FREE_SWAP_PAGES _IO(SNAPSHOT_IOC_MAGIC, 9)
+#define SNAPSHOT_SET_SWAP_FILE _IOW(SNAPSHOT_IOC_MAGIC, 10, unsigned int)
+#define SNAPSHOT_S2RAM _IO(SNAPSHOT_IOC_MAGIC, 11)
+#define SNAPSHOT_PMOPS _IOW(SNAPSHOT_IOC_MAGIC, 12, unsigned int)
+#define SNAPSHOT_SET_SWAP_AREA _IOW(SNAPSHOT_IOC_MAGIC, 13, \
+ struct resume_swap_area)
+#define SNAPSHOT_IOC_MAXNR 13
+
+#define PMOPS_PREPARE 1
+#define PMOPS_ENTER 2
+#define PMOPS_FINISH 3
+
+/**
+ * The bitmap is used for tracing allocated swap pages
+ *
+ * The entire bitmap consists of a number of bitmap_page
+ * structures linked with the help of the .next member.
+ * Thus each page can be allocated individually, so we only
+ * need to make 0-order memory allocations to create
+ * the bitmap.
+ */
+
+#define BITMAP_PAGE_SIZE (PAGE_SIZE - sizeof(void *))
+#define BITMAP_PAGE_CHUNKS (BITMAP_PAGE_SIZE / sizeof(long))
+#define BITS_PER_CHUNK (sizeof(long) * 8)
+#define BITMAP_PAGE_BITS (BITMAP_PAGE_CHUNKS * BITS_PER_CHUNK)
+
+struct bitmap_page {
+ unsigned long chunks[BITMAP_PAGE_CHUNKS];
+ struct bitmap_page *next;
+};
+
+extern void free_bitmap(struct bitmap_page *bitmap);
+extern struct bitmap_page *alloc_bitmap(unsigned int nr_bits);
+extern sector_t alloc_swapdev_block(int swap, struct bitmap_page *bitmap);
+extern void free_all_swap_pages(int swap, struct bitmap_page *bitmap);
+
+extern int swsusp_check(void);
+extern int swsusp_shrink_memory(void);